Means for producing high-frequency oscillations



W. C. WHITE.

MEANS FOR PRODUCING HIGH FREQUENCY OSCILLATIONS.

APPLICATION men JUNE 3, i918.

Patented Oct. 11, 1921.

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UNITED STATES rANroFFics.

WILLIAM 0. WHITE, Oi SCHEN'ECTADY, NEW YORK, ASSIGNOR TO GENERAL ELEG- TRIC COMPANY, A. CORPORATION OF NEW YORK.

FOR PRODUCING HIGH-FREQUENCY OSCILLATIONS.

Patented Oct. 11, 1921.

Application filed June 3, 1918. Serial No. 237,845.

To all whom it may concern:

Be it known that I, WILLIAM O..WHITE, a citizen of the United Seates, residing at Schenectady, in the county of Schenectady, State of New York, have invented certain new and useful Improvements in Means for Producing High-Frequency Oscillations, of

' which the following is a specification.

My present invention relates to the production of high frequency oscillations by means of an electron discharge relay or amplifier, and more particularly to the application of oscillations thus produced in a radio receiving system of the well-known heterodyne type.

Electron discharge devices of the type comprising an evacuated container inclosing a filamentary cathode, a plate-shaped anode and a rid, interposed between cathode and anode, are well known. Various connections have also been employed with such devices to cause themto operate to produce high frequency oscillations. In all of the connections which have previously been used, however, so far as I am aware, the same fundamental principle has been employed, that is, a portion of the amplified energy in the plate circuit of the device has been fed back to the grid circuit by some form of coupling so as to make the system self-exciting.

In carrying my invention into effect, however, I employ a materially difi'erent principle. I have found that under certain conditions with devices of this type the current in the grid circuit may have a dropping characteristic, that is, as the voltage imthe circuit shall be less than 2 6 where L represents the inductance and C-the capacity of the circuit. Hence in carrying my invention into efi'ect I provide the connections necessary to render the grid circuit resonant and thus cause the roduction of oscillations therein. While t e current in the grid circuit is in all cases comparatively will be small the amplifyceived oscillations may also be impressed upon the grid circuit and the two sets of oscillations be combined in that circuit to reduce -what are technically known as beats These beats willbe reproduced in the plate circuit of the device and produce an audible response in the usual telephone receiver which is included in the plate circuit.

The novel features which I believe to be characteristic of my invention are set forth with particularity in the appended claims. The invention itself, however, both as to its organization and method of operation will best be understood by reference to the followin drawing in which Figure l illustrates iagrammaticallysthe connections Which may be employed in carrying my invention into effect, and Fig. 2 shows a characteristic curve of'the current in the grid circuit of an electron discharge device which is so constructed and adjusted as to be suit able for carrying out my invention.

In the system illustrated in Fig. 1 I have indicated an electron discharge device 1 having the usual filamentary cathode 2, an anode 3 which-may be plate shaped as shown or of any other desired form and a discharge-controlling grid 4.- inclosed in a well evacuated receptacle. The grid circuit of this device includes an inductance 5 and a variable capacit 6. A battery 7 is provided for applylng to the grid a potential at which the operation of the device may be suitable for the desired purpose.

Referring now to Fig. 2 the curve A indicates the current in the grid circuit of the device 1, with varying voltages on the grid.

The abscissee of the curve represent voltage and the ordinates current. It will be noted that over a considerable range of voltage when the grid voltage is negative thecurrent in the grid circuit decreases with an increase of the negativegrid voltage. That is, at the point B on the current curve which represents a very small negative voltage the 5 current in the grid circuit is greater than at the point C, which represents a much larger negative grid voltage. This characteristic of the current curve is probably due to the effect of Slight traces of residual gas in the device and the consequent positive ionization. The greater the negative grid voltage the lower the plate current and therefore the lower the amount of positive ionization in the device due to residual gas therein. As a result, therefore, the {grid current will decrease by reason of the smaller number of positive ions which may reach the grid. 4 v If the battery 7 is of such potential that the grid current will fall upon some portion of the current curve between the points B and C, oscillations will be produced in the grid circuit. The frequency of the oscillations produced may be readily varied by adjusting the condenser 6. Inductances 8 and 9 should be employed in series with battery 7 of such value that there will be no damping of the oscillatin circuit due to the connection of the battery I across the circuit. With the device producin oscillations of the desired frequency osci lations received upon the antenna 10 may be impressed upon the inductance 5 by means of the coupling coil 11 which is included in the antenna circuit. The received oscillations will combine in the grid circuit with the locally produced oscillations in the well-known manner and produce beats. In other words, the potential 0f the grid 4 will oscillate and the amplitude of the oscillations will vary at a frequency corresponding with the beat frequency produced. As a result a beat current will be produced in the plate circuit of the device, energy for which is supplied by the direct current generator 12, and the beatsin the plate current may be detected by the usual telephone receiver 13. The telephone receiver 13 may, if desired, be shunted by a capacity 14 for by-passing the radio frequency component of the current in the plate circuit.

I have found that in most cases fairly high potentials must be employed in the plate circuit in order to secure the desired lar device I have found that a plate potential of about 375 volts was necessary in order to secure the desired operating characteristic.

While I have illustrated only one circuit connection whereby oscillations maybe produced and have indicated but one use for the oscillations. it will be apparent that many modifications in the circuit connection employed as well as in the use to which operation. For example, with one particuthe oscillations are applied may be made without departing from the scope of my invention as set forth in the appended claims.

What I claim as new and desire to secure by Letters Patent of the United States, is z--- 1. Means for producing high frequency oscillations comprising an electron discharge device having an electron emitting cathode, an anode and a discharge controlling grid inclosed in an evacuated receptacle, a plate circuit which includes the cathode and anode of said device and a source of potential, a resonant grid circuit which includes the cathode and grid of said device, said device and its associated circuits being so constructed and adjusted that the current in the grid circuit will vary inversely as the applied potential over a given operating range of negative potential and a source of potential connected to the grid circuit of such value that the normal potential of the grid is within said operating range, whereby oscillations will be produced in said grid circuit independently of any coupling between grid and plate circuits.

2. Means for producing high frequency oscillations comprising an electron discharge device having a plate circuit and a resonant grid circuit, said device and its associated circuits being so constructed and adjusted that the current in the grid circuit will vary inversely as the applied potential over a given operating range of negative potential. and a source of potential connected to the grid circuit of such value that the normal potential of the grid is within said operating range, whereby oscillations will be produced in said grid circuit independently of any coupling between grid and plate circults.

3. The combination in a radio receiving system of an electron discharge device having a plate circuit and a grid circuit which is resonant to a frequency differing by an amount within the range of audibility from the waves to be received, means for impressing received waves' upon said grid circuit, said device and its associated circuits being so constructed and adjusted that the current in the 1 id circuit will vary inversely as the applied potential over a given operating range of negative potential, a source of potential connected to the grid circuit of such value that the normal potential of the grid is within said operating range whereby oscillations will be produced in said grid circuit independently of any coupling between grid and plate circuits which will combine with the received oscillations to produce beats and means for detecting the beats thus produced.

- 4. The combination in a radio receiving system of an electron discharge device having a plate circuit and a grid circuit which is '130 resonant to a different frequency from that of the waves to be received, means for impressing received waves upon said grid circuit, sald device and its associated circuits being so constructed and adjusted that the current in the grid circuit will vary inversely as the applied potential over a given operating range of negative potential, a source of potential connected to the grid circuit of such value that the normal potential of the grid is within said operating range whereby oscillations will be produced in said grid circuit independently of any coupling between grid and plate circuits which will combine with the received oscillations to produce beats and means for detecting. the beats ,thus produced.

5. The combination in a radio receiving system of an electron discharge device hav-' ing a plate circuit and a grid circuit which is resonant to a frequency differing by an amount within the range of audibility from the waves to be received, means for impressing received waves upon said grid circuit, said device and its associated circuits being so constructed and adjusted that the current in the grid circuit will vary inversely as the applied potential over a given operating range of negative potential, a source of potential connected to the grid circuit of such value that the normal potential of the grid is within said operating range whereby oscillations will be produced in said grid circuit independently of any coupling between plate and grid circuit which will combine with the received oscillations to produce beats and means in the plate circuit of the device for detecting the beats thus produced. 6. The method of operating an electron discharge device having an electron emitting cathode, an anode and a discharge controlling grid inclosed in an evacuated receptacle and having a plate circuit and a resonant grid circuit associated therewith which consists in generating high frequency oscillations in said grid circuit independently of any transfer of energy to said grid circuit from other circuits.

7. The method of receiving signals in a receiving system comprising an electron emitting cathode, an anode and discharge controlling grid inclosed in an evacuated receptacle and having a plate circuit and a' resonant grid circuit associated therewith which consists in impressing received signaling currents upon said grid circuit, generating oscillations in said grid circuit of a frequency differing from that of the signaling currents independently of any transfer of energy to said grid circuit and thereby producing a beat current in said grid circuit and amplifying and detecting the beats thus produced.

8. The method of operating a signal receiving system comprising an electron emitting cathode, an anode and a discharge controlling grid inclosed in an evacuated receptacle and having a plate circuit and a resonant grid circuit containing a source of energy associated therewith which consists in generating high frequency oscillations in said grid circuit independently of any transfer of energy to said grid circuit from other circuits, and producing by the conjoint action of the locally generated oscillations and received oscillations an audio frequency current in the plate circuit.

In witness whereof, I have hereunto set my hand this 1st day of June, 1918.

, WILLIAM C. WHITE. 

